Nudibranchs (small)

Nudibranchs are soft-bodied, marine gastropod mollusks which shed their shells after their larval stage. They are often referred to as "sea slugs." But, they are noted for their extraordinary colors and striking forms.
There are more than 3,000 described species of nudibranchs, living at virtually all depths of salt water. They can be found in seas worldwide, including both the tropics and Antarctica.